This invention relates generally to aircraft control systems and more particularly to aircraft control systems adapted for propeller driven aircraft used in the initial phase of jet pilot training.
As is known in the art, a jet pilot student typically begins the flight training process on a propeller driven aircraft. It is desirable that the propeller driven aircraft provide speed and power characteristics of a jet. Therefore, a powerful propeller aircraft, having power to weight and power to wing area ratios large compared to a typical single propeller driven aircraft, is typically used during the initial phase of the training process. However, with such a powerful propeller driven aircraft, changes in power, airspeed, or altitude have a pronounced effect on the rudder trim conditions required to maintain the aircraft in coordinated flight. More specifically: (1) When a single propeller aircraft is throttled, the rotational effect of the propeller produced "propwash" i.e., an airflow around the aircraft that swirls, or spirals, downstream to engage the tail section thereby producing lateral forces on the tail requiring a change in the rudder position in order to maintain coordinated flight; and, (2) Because of gyroscopic effects associated with the rotating engine mass (i.e., primarily the propeller), the aircraft precesses during aircraft pitch rate changes requiring pilot rudder movement to maintain coordinated flight. These pilot activity requirements are not characteristic of a jet aircraft. Therefore, these two effects (i.e., throttling and gyroscopic) effects are annoying to an inexperienced student pilot, as well as to the pilot's trainer, particularly in view of the extensive amount of power, airspeed and altitude change that occur during a typical training mission. Such effects are also annoying because of the additional rudder activity required by the student to accomplish acceptable acrobatic maneuvering during the training process. Therefore, requiring the student to counteract these effects in this phase of the training process has been considered, by some trainers, as "negative training" because they are not characteristic of a jet aircraft.
Reducing the throttling effect has been suggested by providing a trim aiding device that, based on flight test results, determines the rudder trim for a variety of power, airspeed and altitude conditions.